Heartworm preventatives are medications designed to protect pets, especially dogs and cats, from heartworm disease, which is caused by parasitic worms transmitted through mosquito bites. These preventatives work by killing the immature larvae of the heartworm before they can develop into adult worms, which can cause serious health issues. Typically available in the form of chewable tablets, topical treatments, or injections, heartworm preventatives should be administered monthly or annually, depending on the product. Regular veterinary check-ups are essential to ensure that pets remain heartworm-free and to monitor for any potential side effects from the medications.